Polymer theranostics with multiple stimuli-based activation of photodynamic therapy and tumor imaging

Background: Efficient theranostic strategies concurrently bring and use both the therapeutic and diagnostic features, serving as a cutting-edge tool to combat advanced cancers. Goals of the Investigation: Here, we develop stimuli-sensitive theranostics consisting of tailored copolymers forming micellar conjugates carrying pyropheophorbide-a (PyF) attached by pH-sensitive hydrazone bonds, thus enabling the tumor microenvironment-sensitive activation of the photodynamic therapy (PDT) effect, fluorescence or phosphorescence. Results: The nanomedicines show superior anti-tumor PDT efficacy and huge tumor-imaging potential, while reducing their accumulation, and potentially side effects, in the liver and spleen. The developed theranostics exhibit clear selective tumor accumulation at high levels in the mouse sarcoma S180 tumor model with almost no PyF found in the healthy tissues after 48 h. Once in the tumor, illumination at λexc = 420 nm reaches the therapeutic effect due to the 1O2 generation. Indeed, an almost complete inhibition of tumor growth is observed up to 18 days after the treatment. Conclusion: The clear benefit of the specific PyF release and activation in the acidic tumor environment for the targeted delivery and tissue distribution dynamics was proved. Conjugates carrying pyropheophorbide-a (PyF) attached by pH-sensitive hydrazone bonds showed their excellent antitumor PDT effect and its applicability as advanced theranostics at very low dose of PyF.

The reaction mixture was bubbled with argon and the polymerization was carried out in a thermostat-controlled water bath at 30 °C for 72 h.The polymer was isolated by precipitation into a mixture of dry acetone and dry diethyl ether (2/1, v/v; 500 mL) followed by centrifugation at 7800 rpm for 3 min.The crude polymer was filtered off, purified by reprecipitation from methanol, filtered, and dried under vacuum (1.44 g, 77 %).The trithiocarbonate end groups were removed via reaction with an excess of 2,2′-azobisisobutyronitrile (AIBN), as previously described [6].AIBN (287 mg) was added into a solution of polymer (1.43 g) in dry DMA (11 mL) and bubbled with argon.After 3 h in a thermostat-controlled water bath at 80 °C, the solution was isolated as described above.The precipitate was dried under vacuum, resulting in the polymer with protected hydrazide groups (1.3 g, 91 %).Boc groups were removed in Q-H2O at 100 °Cas previously described [7].After 2 h, the solution was freeze-dried, resulting in P1 with reactive hydrazide groups (1.12 g, 87 %) (Fig. S1).

Figure S3. 3 .
Figure S3.3.In vivo PDT effect of P-hyd-dPyF (A), and body weight changes of the mice after the treatment (B, C).The mouse sarcoma S180 solid tumor model was used.See the manuscript for details.The data represent mean ± SD, n = 6-8.

Figure S3. 4 .
Figure S3.4.In vivo PDT effect of P-hyd-dPyF in colon cancer C26 bearing mice.The changes of tumor volumes were shown in (A), and the image of tumors of each group was shown in (B).See the manuscript for details.The data represent mean ± SD, n = 6-8.

Figure S3. 5 .
Figure S3.5.Evaluation of side effects of PDT using P-hyd-dPyF in colon cancer C26 bearing mice.The changes of body weight were shown in (A), and the histological examination (H&E staining) of major organs, i.e., the liver and kidney were shown in (B).See the manuscript for details.The data represent mean ± SD, n = 6-8.

Table of content 1 .
Synthesis of monomers, chain transfer agent and polymer precursors